I'd like to make a derived field that is the gradient of a primitive
field. Is there an example of how I can do this? I'm not sure how to
handle ghost cells for something like this.
I spoke with Jeff and he indicated that there was a vorticity example
somewhere, but I cannot find it.
Thanks.

Hi everyone,
After a bit of discussion on and off the yt-dev list, the mechanism
for interpolation in smoothed covering grids and vertex centered data
has changed in r1734. Previously, it would interpolate logged fields
in log-space -- so, for instance, Density would be interpolated in log
space between adjoining cells, rather than in linear space. At the
end of the interpolation it was restored.
This may result in small changes in results for a small set of
analysis types, but I believe that this change -- to interpolating
exclusively in linear space in the unmodified fields -- is the correct
change to make. To restore the old behavior, a derived field can be
created that operates by returning only the logged fields, and then
requesting smoothed or vertex centered data in that field.
Best,
Matt

Dear all,
I would like to access the gravitational potential and plot its radial
profile. Matthew told me that it was done in the clump finding algorithm
but I don't know how to use it.
I would really appreciate if someone could help me.
Thanks a lot,
Jean-Claude

Hi, all--
I've used set_field_parameter for computing quantities, but that works
directly on a ExtractedRegions and whatnot. Is it possible to tie
something directly to the hierarchy or pf so that any new objects I
create can also see this value?
Thanks,
d.
--
Sent from my Stone Tablet and carried by my Pterodactyl.

Dear wonderful YT genii,
Within the star particle routine I am using, when star particles merge they
are kept and have mass set to tiny_mass rather than being deleted. This
makes keeping track of specific particles easier but makes plotting harder.
Does anyone have any good ideas for how to modify or create a new
p.modify["particles"] that will only plot particles above a certain mass?
many thanks,
Libby
--
Elizabeth Harper-Clark MA MSci
PhD Candidate, Astrophysics, UofT
www.astro.utoronto.ca/~h-clark
h-clark(a)cita.utoronto.ca
AIM: edphc1
MSN: edphc1(a)hotmail.com
Skype: eharperclark
Office phone: 416-978-5759

Hi Andy,
On Thu, May 13, 2010 at 6:44 PM, Andrew Cunningham
<ajc4(a)pas.rochester.edu> wrote:
> For some reason I get .yt files on kraken, but on ranger .yt files are never
> saved. ... Do you have any pointers to diagnose why the .yt files aren't
> working on ranger?
This is a weird one. I don't have a good idea. Did you build yt on
Ranger from the install script? Does it mention anything about
serialization when you run scripts? It's possible, I suppose that
seralization has been turned off somehow. Can you add
from yt.config import ytcfg
ytcfg["lagos","serialize"] = 'True'
to your script on ranger to explicitly turn on serialization?
I'm bouncing this to the yt-users list in case someone else might have
had a similar issue on Ranger. I don't use the machine myself, so I
don't have a feel for anything specific to that machine.
Jeff

Hi all,
Is it possible to make something like a derived field in yt that takes
passed variables? A simple example would be extracting gas density
above a certain temperature, but changing that temperature threshold on
the fly
def _hotgas(field, data, temperature_threshold):
reutrn data["density"]*(data["Temperature"] > temperature_threshold)
add_field("hotgas", function=_hotgas, Something else goes here?)
In this particular case I only need a few temperatures and can make a
new derived quantity each time, but it seems like a generally useful
ability.
Thanks,
Charles